How can I create a jar file?

When you say you have java installed, you mean the java development kit right? just installing the java runtime which is all you need to run java applets is not enough, jar is a program inside of the jdk. make sure THIS is what you got: http://java.sun.com/javase/downloads/widget/jdk6.jsp its about 76mb, the java runtime is much smaller ,like around 10mb If you're sure you have the JDK, then you must not have jar in your path, do a search on your computer for jar or jar.exe and then from the command line you want to go into that folder and then type jar, then you want to add whatever folder jar is located in to your path so that you can run jar no matter what folder you're in. here's how to add a folder to your path: http://www.windowsitpro.com/article/configuration/how-can-i-add-a-new-folder-to-my-system-path-.aspx

you have to install java for that

I can't remember whether or not the jar tool comes with the JDK or JRE. I think you have to have the JDK installed. If you're on windows, which it sounds like you are, you will need to modify your PATH environment variable to include the directory that jar is in. This will usually be something like C:\<path to jdk>\bin.

1) Find the directory where java is installed. Let us assume it is C:\java. Then go to C:\java\bin. If you find jar.exe in this bin directory, then you are good. 2) Set the path to the java bin directory. 3) Then try to type jar in your command prompt. To set your path: there are several ways. 1) To set it from command prompt, in the command prompt type SET PATH=%PATH%;C:\java\bin 2) Then hit enter 3) Note: if you have installed java in a different directory type that directory name. I have just provided C:\java as an example. If you don’t find the jar.exe in your java’s bin directory, then you need to uninstall java and install the JDK (not just the JRE). You need JDK for jar. You must have a copy of the Java Runtime Environment (JRE) on your system to run Java applications and applets. To develop Java applications and applets, you need the Java Development Kit, which includes the JRE Here is the link to download java. http://java.sun.com/javase/downloads/index.jsp